Electrochemical/electrocon trollable device electrode

ABSTRACT

An electrochemical/electrically controllable device including at least one carrier substrate provided with an electroactive layer or a stack of electroactive layers placed between a lower electrode and an upper electrode. The upper electrode includes at least one electronically conductive layer, especially a transparent one, based on doped indium oxide or on doped tin oxide or on doped zinc oxide, which is at least partially crystallized in the form of crystallites having a mean size of between 5 and 100 nm, especially between 10 and 50 nm.

The subject of the present invention is an electrochemical and/orelectrically controllable device of the glazing type and having variableoptical and/or energy properties, or a photovoltaic device or else anelectroluminescent device.

At the present time there is in fact an increasing demand for so-called“smart” glazing capable of meeting the requirements of users.

There is also an increasing demand for photovoltaic glazing, which makesit possible to convert solar energy into electrical energy, and forelectroluminescent glazing, which has useful applications in devices andas eluminating surfaces.

As regards “smart” glazing, this makes it possible to control the solarheat influx through glazing panels fitted on the outside of buildings,or vehicles of the car, train or plane type. The object is to be able tolimit excessive heating inside passenger compartments/rooms, but onlyshould there be strong sunlight.

This may also control the degree of vision through glazing panels,especially in order to darken them, or to make them diffusing or even toprevent any vision when this is desirable. This may relate to glazingpanels fitted into internal partitions in rooms, trains or aircraft, orfitted as side windows in motor vehicles. This also relates to mirrorsused as rear-view mirrors, to prevent drivers from being dazzled, orroad signs so that messages appear when necessary, or intermittently inorder to draw the attention better. Glazing panels that can be madediffusing at will may be used, when so desired, as projection screens.

There are various electrically controllable systems allowing this kindof modification in appearance/thermal properties.

To modulate the light transmission or the light absorption of glazing,there are viologen-based systems such as those disclosed in the U.S.Pat. No. 5,239,406 and EP-612 826.

To modulate the light transmission and/or the thermal transmission ofglazing panels, there are also electrochromic systems. As is known,these generally comprise two layers of electrochromic material which areseparated by an electrolyte layer and flanked by two electronicallyconductive layers. Each of the layers of electrochromic material caninject/eject cations and electrons, the change in their degree ofoxidation following such injection/ejection resulting in a change in itsoptical and/or thermal properties. In particular, it is possible tomodulate their absorption and/or their reflection for wavelengths in thevisible or in the solar spectrum.

It is customary to put electrochromic systems into three categories:

-   -   that in which the electrolyte is in the form of a polymer or a        gel; for example, a protonically conductive polymer such as        those disclosed in patents EP-253 713 or EP-670 346, or a        polymer conducting by lithium ions, such as those disclosed in        patents EP-382 623, EP-518 754 and EP-532 408; the other layers        of the system generally being inorganic in nature;    -   that in which the electrolyte is an essentially inorganic layer.        This category is often referred to as an “all solid state”        system—examples of this may be found in the patents EP-867 752        and EP-831 360 and the patents WO 00/57243 and WO 00/71777; and    -   that in which all of the layers are based on polymers, this        category being often referred to as an “all polymer” system.

There are also systems called “optical valves”. These are filmscomprising a matrix of a generally crosslinked polymer, in whichmicrodroplets containing particles are dispersed, which particles arecapable of being oriented in a preferred direction under the action of amagnetic or electric field. Thus, the patent WO 93/09460 discloses anoptical valve comprising a polyorganosilane matrix and polyiodide-typeparticles which intercept much less light when the film is undervoltage.

Mention may also be made of liquid-crystal systems, operating in asimilar mode to the previous ones. They are based on the use of a filmplaced between two conductive layers and based on a polymer in whichliquid-crystal droplets are placed, especially nematic liquid crystalsof positive dielectric anisotropy. When a voltage is applied to thefilm, the liquid crystals orient along a preferred axis, which permitsvision. With no voltage applied, when the crystals are not aligned, thefilm becomes scattering and prevents vision. Examples of such films aredisclosed in particular in European patent EP-0 238 164 and U.S. Pat.No. 4,435,047, U.S. Pat. No. 4,806,922 and U.S. Pat. No. 4,732,456. Thistype of film, once it has been laminated and incorporated between twoglass substrates, is sold by Saint-Gobain Vitrage under the brand name“Priva-Lite”.

In fact, it is possible to use any of the liquid-crystal devices knownby the term NCAP (Nematic Curvilinearly Aligned Phase) or the term PDLC(Polymer Dispersed Liquid Crystal).

It is also possible to use, for example, cholesteric liquid-crystalpolymers such as those disclosed in the patent WO 92/19695.

As regards electroluminescent systems, these include a phosphor materialsupplied with electricity via electrodes.

All these confounded systems have in common the need to be equipped withcurrent leads for supplying electrodes generally in the form of twoelectronically conductive layers on either side of the active layer orof the various active layers of the system.

These electronically conductive layers (which may in fact be asuperposition of layers) commonly include a layer based on indium oxide,generally tin-doped indium oxide known by the abbreviation ITO. Theremay also be layers based on doped tin oxide, for example antimony-dopedtin oxide, or else layers based on doped zinc oxide, for examplealuminum-doped zinc oxide (or a mixture based on at least two of theseoxides).

These layers are sufficiently conductive and can be easily deposited bymagnetically enhanced sputtering, either using an oxide target(nonreactive sputtering) or using a target based on indium and tin(reactive sputtering in the presence of an oxidizing agent of the oxygentype).

The objective of the invention is to be able to improve the performanceof electrochemical/electrically controllable systems of the type ofthose (electrochromic, photovoltaic, electroluminescent, etc.) describedabove, and more particularly electrochromic systems, especially theiroptical/energy performance and their switching rate, and/or to extendtheir lifetime. Secondarily, this objective is to be achieved withoutupsetting the known configurations of electrochemical systems relatingto the invention. More generally, the aim is to develop betterelectrodes on an essentially transparent (glass or polymer) substrate.

The subject of the invention is an electrochemical/electricallycontrollable device having variable optical and/or energy properties,comprising at least one carrier substrate provided with an electroactivelayer or a stack of electroactive layers placed between an electrodecalled the “lower” electrode and an electrode called the “upper”electrode. According to the invention, the “upper” electrode comprisesat least one electronically conductive layer, preferably transparent,based on doped indium oxide, especially tin-doped indium oxide, or ondoped tin oxide, especially antimony-doped tin oxide, or on doped zincoxide, especially aluminum-doped zinc oxide. Said layer is at leastpartially crystallized in the form of crystallites having a mean size ofbetween 5 and 100 nm, especially at least 20 nm . The invention may infact apply more generally to the conductive layers referred to as TCO(Transparent Conductive Oxide) layers, that is to say transparentconductive layers based on one or more metal oxides.

Within the context of the invention, the term “lower” electrode isunderstood to mean the electrode lying closest to the carrier substratetaken as reference, on which electrode at least some of the activelayers (all of the active layers in an “all solid state” electrochromicsystem) are deposited. The “upper” electrode is that deposited on theother side with respect to the same reference substrate.

In the rest of the text, for the sake of brevity the layer based onindium oxide or based on tin oxide or based on zinc oxide of the upperelectrode will be denoted by the term “upper ITO”. By convention, thisname also covers indium oxides doped by a metal other than tin.

The inventors have surprisingly discovered the influence that thecrystalline structure of the upper ITO can have on all of the rest ofthe electroactive system. It has turned out that an at least partiallycrystalline structure, additionally having crystallites of nanometricsize, is much more advantageous than, for example, an amorphousstructure.

This “nanocrystallization” of the ITO according to the invention cannotalways be detected by X-ray diffraction. If it cannot be detected byX-rays, other analytical techniques may be used. These include, inparticular, TEM (Transmission Electron Microscopy), or the techniquecalled SAED (Selective Area Electron Diffraction).

In fact, this particular crystallization is beneficial with regard tothe stability of the entire electrochemical system: the upper electrodeis frequently deposited on top of all of the other layers of theelectroactive system by, for example, a vacuum technique of thesputtering type. Consequently, the tendency is therefore to givepreference to “cold” deposition, at room temperature, for at least tworeasons:

-   -   firstly, this thus avoids taking any risk of degrading the        subjacent layers; and    -   secondly, satisfactory levels of electrical conductivity are        obtained “cold”.

Layers of the amorphous type are therefore generally obtained. However,the inventors have shown that it is necessary to take into account notonly the electrical conductivity of the layer but also itselectrochemical stability. Furthermore, upper ITO layers of theamorphous type would, without realizing it, be the cause of prematureinstability and aging of certain electrochemical systems.

In contrast, if the upper ITO layers are deposited so as to be“nanocrystallized”, they are much better and much more electrochemicallystable. This discovery has allowed the performance of electrochemicalsystems, especially in the case of electrochromic systems, to besignificantly improved by increasing their lifetime. By this is meant,in particular, that the period of time until the switching rate startsto fall off can be extended. This may also make it possible to extendthe period of time until the variation in light and/or energytransmission starts to have a smaller amplitude and/or until the lightand/or energy transmission value in a given state starts to drift. Theinventors have also noticed, with this type of upper ITO, theelectrochemical systems are more temperature stable. This is a notinsignificant point, especially for electrochromic glazing panels fittedas outside windows of buildings or as motor vehicle roofs, these glazingpanels being liable to heat up due to the effect of sunshine and oftheir coloration, which makes them (at least slightly) absorbent.

Advantageously, the upper ITO according to the invention has anelectrical resistivity of between 10⁻⁴ and 10⁻² ohm.cm, especially onebetween 10⁻⁴ and 2×10⁻³ ohm.cm, making its use as an electrode perfectlysatisfactory.

Preferably, especially in order to achieve this level of resistivity, ithas a thickness of between 40 and 400 nm, especially between 50 and 300nm or between 120 and 280 nm. Within these thickness ranges, the ITO istransparent, that is to say it has a low light absorption in thevisible. However, it is not excluded from having substantially thickerlayers (especially if the electroactive system of the electrochromictype operates in reflection rather than in transmission), or thinnerlayers (especially when they are combined in the electrode with anothertype of conductive layer, for example a metallic layer).

Advantageously, the ITO contains between 3 and 20%, especially 5 and 15%and preferably about 10%, tin (or another dopant metal) with respect toindium. This percentage is expressed by weight of tin oxide (dopantoxide) with respect to indium oxide (the predominant oxide). Thispercentage range between dopant oxide and predominant oxide ispreferably offset toward lower values when said layer is a layer basedon zinc oxide oxide, especially aluminium-doped zinc oxide; in thiscase, a percentage by weight of Al₂O₃ of between 0.5 and 5%, especially1 and 4%, with respect to ZnO is preferred. One example consists inchoosing a proportion of 2% by weight of Al₂O₃ with respect to ZnO.

According to a variant of the invention, the lower electrode alsoincludes an electronically conductive layer, preferably transparent andbased on a conductive oxide of the same type as that of the upperelectrode, such as doped indium oxide, especially tin-doped indiumoxide, or doped tin oxide or doped zinc oxide, and at least partiallycrystallized, like that belonging to the upper electrode. It is thuspossible to have two layers based on ITO or on tin oxide or on zincoxide, one in each of the two electrodes of the electroactive system,and having the same characteristics. This has in particular theadvantage of being able to deposit a succession of layers, one after theother, the first and the last (the ITO or doped tin oxide or doped zincoxide layers) being deposited in the same way, with the same depositionparameters (especially in the same deposition chamber when this iscarried out by sputtering, by making the carrier substrate pass twicebeneath the same target with the same conditions/settings.

Preferably, the upper electrode according to the invention includesother conductive elements than the upper ITO: more particularly, it ispossible to combine the ITO layer with a layer more conductive than thelatter and/or with a plurality of conducting bands or wires. For furtherdetails, reference may be made to the aforementioned patent WO 00/57243for the implementation of such multi-component electrodes. A preferredembodiment of this type of electrode consists in applying, to the ITOlayer (optionally surmounted by one or more other conductive layers), anarray of conducting wires embedded in the surface of a sheet of polymer(which may then protect the active system and/or allow the glass-typecarrier substrate to be laminated to another glass in the case of themanufacture of an electroactive glazing panel, for example of theelectrochromic type).

As mentioned earlier, the invention may apply to various types ofelectrochemical or electrically controllable systems. It is moreparticularly of interest in the case of electrochromic systems,especially “all solid state” or “all polymer” systems or elseliquid-crystal or viologen-based systems, or electroluminescent systems.

The electrochromic systems or glazing panels to which the invention mayapply are described in the aforementioned patents. They may comprise atleast one carrier substrate and a stack of functional layers comprisingat least, in succession, a first electronically conductive layer, anelectrochemically active layer capable of injecting or ejecting ions,such as H⁺, Li⁺, OH⁻ of the anodic or cathodic electrochromic materialrespectively, an electrolyte layer, a second electrochemically activelayer capable of injecting or ejecting ions such as H⁺, Li⁺, OH⁻ of thecathodic or anodic electrochromic material respectively, and a secondelectronically conductive layer (the term “layer” is to be understood tobe a single layer or a superposition of several, continuous ordiscontinuous, layers).

The invention also relates to the incorporation of the electrochemicaldevices described in the preamble of the present application in glazing,operating in reflection (a mirror) or in transmission. The term“glazing” is to be understood in the broad sense and it encompasses anyessentially transparent material, made of glass and/or polymer (such aspolycarbonate PC or polymethyl methacrylate PMMA). The carriersubstrates and/or superstrates, that is to say the substrates flankingthe active system, may be rigid, flexible or semi-flexible.

If the glazing operates in reflection, it may especially be used as aninterior mirror or as a rear-view mirror.

The invention also relates to the various applications in which thesedevices may be found—glazing or mirrors: they may be glazing forbuildings, especially external glazing, internal partitions or glazeddoors. They may also be windows, roofs or internal partitions for meansof transportation such as trains, aircraft, cars, ships. They may alsobe display screens, such as projection screens, television or computerscreens, and touch-sensitive screens. They may also be used to makespectacles or camera lenses, or to protect solar panels. They may alsobe used as energy storage devices of the battery or fuel-cell type, andas batteries and cells themselves.

The subject of the invention is also the process for obtaining thedevice described above, consisting in depositing the upper ITO bymagnetically enhanced sputtering, especially at room temperature. Thisis because it is often chosen to deposit the ITO layer of the lowerelectrode hot, as this is the first layer of the stack and thisgenerally makes it possible to obtain denser layers. However, for theupper ITO, deposition at room temperature is preferable so as to avoidhaving to heat the subjacent layers, which are liable to be damaged athigh temperature. However, heating to moderate temperatures (30 to 220°C., especially 50 to 200° C.) is possible, or even to highertemperatures, if the subjacent layers are able to withstand thesetemperatures.

Advantageously, the pressure in the deposition chamber during depositionof the upper ITO is less than 1.2 Pa (1.2×10⁻² mbar), preferably lessthan or equal to 1 Pa (10⁻² mbar) or less than or equal to 0.8 Pa(8×10⁻³ mbar) or less than or equal to 0.5 Pa (5×10⁻³ mbar).Advantageously, the pressure is at least 0.08 Pa (8×10⁻⁴ mbar): it hasbeen shown that depositing the upper ITO layer at such low pressuresmakes it possible to obtain a dense nano-crystallized layer. Accordingto the invention, there are other techniques, again using sputtering, toachieve this result; thus, it is possible to use deposition with ionassistance, to use off-equilibrium magnets and/or, as was seen above, toheat (moderately) the carrier substrate during deposition.

Advantageously, the functional layer (or the stack of functional layers)and the upper ITO (and even possibly the lower electrode) are depositedby the same deposition technique. This is especially the case for “allsolid state” electrochromic systems.

The invention will now be described in greater detail with the aid ofnonlimiting examples and the figures:

FIG. 1: a schematic sectional view of an electrochromic cell using anupper ITO according to the invention;

FIG. 2: a graph comparing the aging of electrochromic cells using upperITO layers in accordance with the invention with amorphous upper ITOlayers; and

FIG. 3: electron diffraction patterns of the upper ITO according to theinvention and according to a comparative example.

FIG. 1 is intentionally highly schematic and is not necessarily to scalein order to make it easier to examine: it represents, in cross section,an “all solid state” electrochromic cell comprising, in succession:

-   -   a pane 1 of clear soda-lime silica glass 2.1 mm in thickness;    -   a lower electrode 2, which is a bilayer consisting of a 30 nm        SiO_(x)N_(y) first layer surmounted by a 250 nm ITO (tin-doped        indium oxide) second layer;

The electrochromic system 3 comprises:

-   -   a first layer of anodic electrochromic material consisting of 40        to 100 nm of hydrated iridium oxide or 40 to 400 nm of hydrated        nickel oxide which may or may not be alloyed with other metals;    -   a layer consisting of 100 nm of tungsten oxide;    -   a second layer consisting of 100 nm of hydrated tantalum oxide        or hydrated silica oxide or hydrated zirconium oxide;    -   a second layer consisting of 370 nm of cathodic electrochromic        material based on tungsten oxide WO₃;    -   an upper electrode 4 consisting of a 270 nm ITO layer 5 and an        array of conducting wires 6 encrusted in the surface of a sheet        7 of polyurethane PU 1.24 mm in thickness. The conducting wires        are made of metal, parallel to one another and linear.        Alternatively, these wires may be in a wavy pattern.

The PU sheet 7 is used to laminate the glass pane 1 to another glasspane 8 having the same characteristics as the glass pane 1. Optionally,that face of the glass pane 8 facing the PU sheet 7 is provided with astack of thin layers having a solar protection function. This stack mayinclude in particular, in a known manner, two silver layers sandwichedby dielectric layers.

All of the layers were deposited by magnetically enhanced sputtering.The lower ITO was deposited hot, at 300° C.

EXAMPLE 1

In this case, the ITO of the upper electrode was deposited at roomtemperature, the pressure in the deposition chamber being 0.4 Pa (4×10⁻³mbar), using a target made of fully oxidized ITO ceramic comprisingabout 10% by weight SnO₂ with respect to In₂O₃. The ITO layer wasanalyzed by electron diffraction: the pattern in FIG. 3 a clearly showsspots characteristic of nanometric-size crystallites.

EXAMPLE 2 (COMPARATIVE EXAMPLE)

In this case, the ITO of the upper electrode was deposited at roomtemperature, the pressure in the deposition chamber being 1.2 Pa(1.2×10⁻² mbar), using the same target as that of example 1. The ITOlayer was analyzed as in example 1: the pattern in FIG. 3 b shows theabsence or virtual absence of spots, this being characteristic of anessentially amorphous morphology.

Comparative tests were carried out on the two electrochromic cells.

Firstly, the influence of the morphology of the upper ITO on thevariation in a parameter called the “characteristic resistance” as afunction of time was studied. This characteristic resistance CR is infact the inverse of the switching speed when a given voltage is appliedto the terminals of the electrodes. It is also possible to determinewhen the system starts to “age”.

The results are shown in FIG. 2: plotted on the x-axis is therefore thetime in hours, and the CR is plotted on the y-axis with a scale rangingfrom 0 to 160. The tests were carried out by cycling the electrochromiccells in a dry oven at 5% relative humidity and at 80° C.

The curve formed by the circles corresponds to comparative example 2 andthe curve formed from the diamonds corresponds to example 1 according tothe invention: it may be seen that the curve corresponding to example 2rapidly starts to drift after the first hundred hours of use. Incontrast, the curve corresponding to the example according to theinvention is remarkably flat up to 2000 hours, and, from 2000 to 4000hours it tends to increase, but very modestly: this is an exceptionalresult and proves the importance, hitherto unsuspected, of themorphology of the upper ITO.

Another test was carried out, consisting in measuring the variation inlight transmission ΔT_(L) in %, under illuminant D₆₅) between t=0 andt=30, 500, 1000 and 5000 hours, when the cells are locked in the coloredstate. The results are given in table 1 below: TABLE 1 T (hours ΔT_(L)(example 1) ΔT_(L). (comparative example 2) 30 −2 −12 500 −6 −15 1000 −6−16 5000 −8 −17

Here again, it may be seen that the example according to the inventionis much better, with a T_(L) drift that remains less than 10% after 5000hours of use. The drift is also gradual. In contrast, the comparativeexample has already drifted by more than 10% by 30 hours of use.

These results show the importance of electrochemically stabilizing thisupper ITO layer by crystallizing it and densifying it; it is probablethat the crystallization of the layer is critical as it organizes thestructure of the oxide, making it denser and therefore more stable (thecrystallographic cell of the ITO is cubic, with a lattice parameter of10.226 ångströms).

Useful results are also obtained with upper (possibly also lower)electrodes based on aluminum-doped zinc oxide.

The invention also relates to the substrate provided with at least oneelectrode of the type described above, independently of theelectrical/electrochemical device in which it is incorporated orintended to be incorporated.

1-16. (Canceled).
 17. An electrochemical/electrically controllabledevice having variable optical and/or energy properties, comprising: atleast one carrier substrate provided with an electroactive layer or astack of electroactive layers placed between a lower electrode and anupper electrode; wherein the upper electrode comprises at least onefirst electronically conductive layer, especially a transparent one,based on doped indium oxide, especially tin-indium oxide, or on dopedtin oxide or doped zinc oxide, which is at least partially crystallizedin a form of crystallites having a mean size of between 5 and 100 nm,especially between 10 and 50 nm, especially at least 20 nm.
 18. Thedevice as claimed in claim 17, wherein the first electrically conductivelayer based on doped indium oxide or on tin oxide or on zinc oxide ofthe upper electrode is predominantly crystallized.
 19. The device asclaimed in claim 17, wherein the first electrically conductive layerbased on doped indium oxide or on tin oxide or on zinc oxide of theupper electrode has an electrical resistivity of between 10⁻⁴ and 10⁻²ohm·cm, especially between 10⁻⁴ and 2×10⁻³ ohm·cm.
 20. The device asclaimed in claim 17, wherein the first electrically conductive layerbased on indium oxide has a thickness of between 40 and 400 nm,especially between 50 and 300 nm.
 21. The device as claimed in claim 17,wherein the first electrically conductive layer based on indium oxide ofthe upper electrode contains between 5 and 15% tin oxide by weight withrespect to indium oxide.
 22. The device as claimed in claim 17, whereinthe first electrically conductive layer is based on aluminum-doped zincoxide and contains between 0.5 and 5% by weight of aluminum oxide withrespect to zinc oxide.
 23. The device as claimed in claim 17, whereinthe lower electrode comprises a second electronically conductive layer,especially a transparent one, based on doped indium oxide, especiallytin-doped indium oxide, or on doped tin oxide or doped zinc oxide, andat least partially crystallized like the first electrically conductivelayer forming part of the upper electrode.
 24. The device as claimed inclaim 17, wherein the upper electrode comprises, apart from the firstelectrically conductive layer based on doped indium oxide, at least oneother electronically conductive layer and/or a plurality of conductingbands or conducting wires.
 25. The device as claimed in claim 17, as anelectrochromic system, especially an all solid state electrochromicsystem or an all polymer electrochromic system or a liquid-crystalsystem or a viologen-based system, or an electroluminescent system. 26.A glazing panel incorporating the device as claimed in claim
 17. 27. Amirror, especially a rear-view mirror, incorporating the device asclaimed in claim
 17. 28. The use of the device as claimed in claim 17for making glazing panels for buildings, glazing panels equippinginternal partitions or windows or roofs or equipping means oftransportation of an aircraft, train, automobile, or ship type, displayscreens, such as computer or television screens, or projection screensand touch-sensitive screens, and for making spectacles or lenses orphotographic equipment or solar panel protection means, or illuminatingsurfaces.
 29. A process for obtaining the device as claimed in claim 17,wherein the first electrically conductive layer based on doped indiumoxide or on doped tin oxide or on doped zinc oxide of the upperelectrode is deposited by magnetically enhanced sputtering, especiallyat room temperature.
 30. The process as claimed in claim 29, wherein apressure in a deposition chamber during deposition of saiddoped-oxide-based first electrically conductive layer is less than 1.2Pa and preferably less than or equal to 1 Pa or 0.8 Pa.
 31. The processas claimed in claim 29, wherein said coped-oxide-based firstelectrically conductive layer is deposited with ion assistance and/oruse of off-equilibrium magnets and/or heating during the deposition. 32.The process as claimed in claim 29, wherein the electroactive layer orthe stack of electroactive layers and the first electrically conductivelayer based on doped indium oxide or doped tin oxide or doped zinc oxideare deposited by sputtering.